Active cooling systems, such as fans, face multiple challenges when implemented in ultrathin devices, such as tablet or laptop computers. General Electric (GE) has developed a cooling device using two piezoelectric membranes, called a Dual Piezoelectric Cooling Jet (DCJ). The piezoelectric membranes are electrically activated, causing them to expand and contract, forming a cavity that spills air at a high velocity, for example, like a bellows. However, the DCJ is an energy intensive device, and a DCJ driver may be large and expensive. Further, the DCJ membranes operate like a speaker/transducer, so that any oscillations within the human hearing band (approximately 200 Hz to 20 KHz), for example, due to noise or distortion in the driver signal, may be audibly detected.
FIG. 19 shows a prior art topology for a single-phase voltage source inverter for renewable energy sources. The circuit includes an input stage, a buck-boost stage, and an unfolding stage. It was implemented in discrete parts due to the high power to process. This circuit is based on a typical PI controller or Energy controller and very low fixed frequency switching. This typically leads to very high distortion level (>5%), low power efficiency at low power output and very limited boost voltage ratio ≈3.5 (Vout/Vin). Therefore, there is a need in the industry to address one or more of the abovementioned shortcomings.